SHRINKAGE OF CORONAL X-RAY LOOPS

We present the first set of examples of the shrinkage of large-scale n onflare loops in the solar corona, observed by the Yohkoh Soft X-Ray T elescope in 1993 February. A large and isolated active region exhibite d an unusual south-north asymmetry in coronal dynamics and heating. Th e northern part, referred to the main magnetic axis, showed episodic e xpansion and heating. In contrast, the southern part displayed obvious shrinking and cooling. This asymmetry was correlated with a severe as ymmetry in the surface magnetic activity revealed by Huairou vector ma gnetograms. Observations suggest that this shrinkage is not an apparen t motion, but a real contraction of coronal loops that brighten as a r esult of heating at footpoints followed by gradual cooling.